Because of the height reached by wind turbines and their location on elevated areas, they have a high risk of receiving lightning strikes particularly at its blades. Therefore the blades must have a lightning protection system and any additional system installed in them containing conductive elements (metal parts, sensors, beacon systems, etc.) must be protected against direct lightning strikes and indirect effects due to the electromagnetic field induced by them.
The primary components of lightning protection system for wind turbine blades are a series of metal receptors mounted on the surface of the blade and a down conductor to drive the lightning from the receptors to the blade root. The evolution in wind turbines development together with the growth of the power provided by them has led to new generations of wind turbines having increasing dimensions both in tower height and rotor diameter. Blade lengthening involves an increase in rigidity. The use of more carbon fiber laminates in the manufacturing of blades is a conventional way to achieve this rigidity. However, carbon fiber laminates are conductors and must therefore be connected in parallel with the down conductor of the lightning protection system to prevent internal arcing between the down conductor and the laminates as well as direct lightning strikes on the carbon laminates.
WO 2006/051147 A1 describes a lightning protection system comprising means for equipotentializing the carbon fiber laminates with the down conductor including auxiliary cables to connect directly the down conductor with the carbon fiber laminates. These auxiliary cables are connected using a joint screwed to a metal plate in direct contact with the layers of carbon fiber. The electrical connection can be improved by adding conductive resins to the joint area.
ES 2 396 839 describes a lightning protection system for a wind turbine blade formed by various connections arranged on the carbon fiber laminates of the blade equipotentializing the surface of beam flanges through derivations of a primary cable by means of auxiliary cables and a high inductance device mounted on the connection between the carbon fibre laminates and the primary cable to reduce the passage of current across the carbon laminates and favour the conduction through the primary cable.
While the installation of the abovementioned lightning protection systems in wind turbine blades of a conventional structure does not pose problems it does not happen the same in the case of wind turbine blades with structural shells.
The present invention is directed to solving that problem.